Abstract. An important tendency over the past years in the conventional cultivation of crops is the reduced use of synthetic products. The experiment was carried out in the period 2014–2015 at the Institute of forage crops (Pleven) and aimed to study the biological performances of alfalfa after application of mineral oil Akarzin, either alone and in combination with reduced doses of synthetic insecticide (Eforia 045 ZC). The alone and combined use of Akarzin had no phytotoxic effect on the crop and influenced positively on the relative water content and dry mass productivity (an increase by 5.2 to 8.7 % and by 10.1 to 29.2 %, respectively). The treatment with the synthetic products also had a favorable effect on the phytosanitary status of the crop and restricted the аttack by Pseudopeziza medicaginis. The combined application of Akarzin along with Eforia 045 ZC allowed reducing the applied dose of the insecticide up to 0.03 and 0.01 %, as the same time the achieved effect in regard to the productivity exceeded the one of self–application of Eforia 045 ZC in the highest dose (0.05 %). With a view to reducing the negative impact on environment a reduction of the application dose of the insecticide after combining it with the mineral oil is recommended as an environmentally friendly approach in conditions of conventional cultivation of alfalfa.